Magnetically biased switch



Sept 26 1961 J. A. BALDWIN, JR., ETAL 3,002,067

MAGNETICALLY BVIASED SWITCH Filed July 1, 1959 J A. BALDWIN JR. A

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A Tron/ver United States vPatent i 3,002,067 f MAGNETICALLYBISED S -CH'John A. "Baldwin, J r., `Murray ltlillpmd Alexander "Feiner,

Whppany, NJ., t assgnors :to ell Telephone :laboratores, Incorporated,New Ymlk, -of New York n AFiled .Iuly 1,1952, Ser. N0..824,`225 `11Claims. I(Cl. M10-87) i,

This .invention relates 4to .electromechanical switching rdevices andmore particularlyltosuch devcesincombination with permanent magnetcontrol means.

In switching applicatio ns,.such.as 4are encountered, for

example, in telephone systems, .it is necessary to .provide`interconnecting -facilities .which are rugged,y reliable ,and

economical. An` element `which satisfies .these requirepractice theelectromagnetic field may befestablished in ay small fraction of amillisecond. `The relay contacts lon the other hand, require a/signicantly longer time .to respond. Even though the contacts,onceoperated, may be held closed by other means such as mechanical ormagnetic latching arrangements, vthe electromagnetic tiel scss all ofthe desirable-characteristics-of the relay are not f available. n

One solution to this .problem is disclosed in copending Patented Sept.26, ,1961

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y""Iheseand'other objects of thsiinvention are `achieved jn one specificembodiment `thereof which combines a magnetically responsible reedswitch of thetype described in"Development of :Reed Switches and .ReedRelays by `Hovgaard et.al.,`vol. 34 ofthe Bell System' Tech- .nical Iourna1,jpage'309'if., with a,permanent magnetand `a"bistable magneticmember of a material exhibiting two remanent magnetization states.advantage of the `reed switch whichrenders itsuitablelforusein thevinstant `inventionisits ability torespond ,to relativelyweakmagneticffields. The reed switch, being 'hermetically sealed, alsoexhibits good contact.stability .and further possesses a .relatively,short :responsetime inicomparison withmechanical switches Iin general.

The permanent ,magnet .employed `in `this invention is .designed -toexhibit a high `magnetic retentivity. That is,.it.is,composed.of.amaterial exhibiting this characteristic and treated,.as .knowninthefart, ,to maintain a stable :remanent .magnetization -indefinitely.On the .other hand, 20 i the bistable magnetic member of this invention`is com- ;posed .of yamaterial which `:exhibits magnetic retentiw'ty but.which may -Abeswitched .by .the application of a suitr-.able magneticield vto one .or another fof .a plurality of remanent magnetizationstates. The -so-.called square :loop materials, .of which .the .ferritesvare .a class, :possess these characteristics. .Accordinglv yonespecific .embodiymentfoffthis inventionincludes/a'ferrite asthe materialof .the .bistable magnetic member.

lIn this specific embodiment the .permanent magnet and .fthe :bistablemagneticfmemberare positioned adjacent the switch and substantiallyalong van extension of the switch :axis so athat lthe 5magnetizin'gvforce vrproduced'by the mag- .netic member in -one fremanentstatcYreinforces the fmag- (netic riel-d of `the permanent magnet .whilefthemagnetizing .force rproduccd .fin the 'other .such state y.effectivelyvcany;cels;this lield. ln-the .formery case., the'vswitch contacts .arelheldclosed b.y athe field vof the permanent magnet reinforced by themagnetizationgof '.the magnetic grnember; in the :lattercase,the=1switch contacts release because of ithefeld cancellation. M

A second speciiicl embodiment `of .thisssinvention `includes la reedZswitch -of thettype described above, a permanent -magnet `and a4ferrite. member having :a control Winding. The ferrite member andthepermanent magnet Aare positionedadjaccnt the :respective terminals ofthereed switch 4and substantially at yrig'htanglcs to :the jswitch axis:so `as application Serial No. 824,222, tiled July :1, .-1959 .of A. f

Feiner, C. A. Lovell, T. N. Lowryand P. G. Ridinger. Devices disclosedtherein render `the .relatively slow respouse vmechanical switch itselfcompatible with electron*- ic control signals. This compatibilityisachieved by the combination of a bistable remanently magnetic elementresponds to this remanent magnetic condition. Thus, in

a telephone system employing such devices, electronic control equipmentis rnot tied up by #the necessity of vrnaintainingthe magneticitield'ofthe 'relay .until its switch contacts operate. v

The instant `invention provides asimilar `solution tothe problem. Thusit is an object `of this .invention tojprovide an improved mechanicalswitch.

More particularly, it is an object of this .invention to provide a`magnetically responsive lswitch controllable by electronic pulses. n

A further object of this invention is to Y.provide ,a magneticallybiased mechanical switch which Ais `,controllable sby pulses of.duration :less than rtheresponse time of the `switch. n n e fr`toprovide la shorter Apath forfmagnetic :flux than .is permitted inthe first .embodiment of the linvention. `,Connected to the ends of theferrite lmember andthe per- Vnianentfmagnet remote .fromfthe switchterminals Yis a piece Avision of'a low reluctancepathzfor `magneticliux'in place of the longer paths through air inthe specific Iembodimentof the invention described above.

A variation -of this embodiment Isubstitutes ua second reed switch forthe Vpiece -of magnetically permeable material 'connecting the ends ofthe -ferrite lmember and ythe permanent magnet thus Acompleting themagnetic circuit while affording concurrent control of two separateswitch contact pairs.

/Itis a feature of this invention 'that a switching varrangementcomprise a'magnetic circuit including `a relay, a remanently magneticmember and aV permanent magnet.

"It is a feature ,in accordance with .one specific erny bodiment ofthisinvention that the magnetic circuit inm-the permanent magnet and the1 member.

clude apermeable .magnetic member connected between remanently magneticthe order of a few microseconds.

It is another feature in accordance with one specific embodiment of thisinvention that the magnetic circuit comprise a pair of relays connectedat their respective terminals to oppositesides ofthe permanent magnetand the remanently magnetic member. Y

Another feature of this invention is the utilization of the resultantfield of a permanent magnet and one remanent magnetization state of abistable magnetic member to close the contacts of a magneticallyresponsive switch and of the resultant field of the permanent magnet andthe other remanent magnetization state of the bistable magneticmemb'erto open the contacts of the switch.

More generally, it is a feature of this invention that the contacts ofamagnetically responsive switch be actuated under control of `themagnetic field established in a permanent magnet as reinforced orcancelled by the magnetic field selectively established in a bistablemagnetic member.

A complete understanding of this invention and of these and otherfeatures thereof, may be gained from the following detailed descriptionwhen read in connection with the accompanying drawing in which: n

FIG. 1 depicts a view of one specific embodiment of the invention;

FIG. 2 is another view of the specific embodiment of FIG.A1 withportions thereof depicted in cross section;

FIG. 3 is a view of a second specific embodiment of the invention; and

FIG. 4 depicts a variation of the specific embodiment of the inventionshown in `IFIG. 3.

-In FIG. 1 a reed switch 1 is shown having a pair of contact members orreeds 2 attached to opposite terminals 3. A bead-shaped .member 4 of apermanently magnetic material is arranged on one of the terminals 3while a similar bead-shaped member 5 of a different magnetic materialexhibiting two stable remanent magnetization 'states is mounted aroundthe other terminal 3. A conductor 6 is wound on the remanently magneticmember 5.

FIG. 2 represents the same arrangement with the permanent magnet 4 andthe bistable .magnetic member 5 `shown in cross section. The magneticpolarity of the permanent magnet 4 is indicated.

`Current pulses are applied to the winding 6 in order to establish aparticular remanent magnetization state in the bistable magnetic member5. The established remanent magnetization of the member 5 either aids oropposes the indicated magnetic field of the permanent magnet. 4. Whenthe remanent magnetization of the member 5 is such that it tends toproduce a north magnetic pole at the upper end of the member 5 (see FIG.2), the field -of the permanent magnet is reinforced. 'Ihis drives amaximum magnetic flux through the reeds 2 and sets them in the closedposition. When the remanent magnetization of the member 5 is establishedso as to produce a south magnetic pole at the upper end of the member 5,the resultant magnetic field opposes the eld established by thepermanent magnet 4 and is of sufficient current pulses of properpolarity applied to the winding 6. These pulses need only be sufficientin duration to establish the desired state of the bistable magneticmember ,5. For most ferrites thisjresponse time may be of 1 Thereafterthe established remanent magnetization state of the bistable mag- For `areed switch the response time is of the order of milliseconds. Thus iscan be 'seen that netic member 5 causes the reeds 2 to respond as delscribed above.

this invention provides the highly desirable compatibility betweenelectronic switching pulses and a magnetically responsive switch in asimple and effective arrangement. Furthermore, because of the disparityin the response times of the bistable magnetic member 5 and the reedswitch 1, the magnetization state of the member 5 may be reversed anumber of times, if desired, before rthe contact members 2 respond tothe final magnetization state ofthe member 5.

FIG. 3 depicts a second specific embodiment of the invention. In thisfigure, a switch .1 having a pair of reed contacts 2 of a magneticmaterial and a pair of terminals 3 is shown connected to a ferritemember 10 and a permanent magnet 11. A winding 12 is wound about theferrite member 10 to control the remanent magnetization of the member 10in accordance with the direction of current applied to the winding 12.Between the ferrite member 10 and the permanent magnet 11 remote fromthe switch 1, is a rod 13 of a magnetically permeable 4materialproviding a low reluctance path for magnetic finir.v

In accordance with an aspect of the invention the specific embodimentthereof depicted in FIG. 3 advantageously attains an improved operationby providing a shortened path for magnetic flux and further by providingin a portion of this path the lowreluctance material of the rod 13. Thisimproves the sensitivity of the inventive structure by increasing thestrength of the combined magnetic fields of the ferrite member 10 andthe permanent magnet 11 for operating the reed switch 1. FIG. 4 depictsa variation of the specific embodiment 'of the invention which isdepicted in FIG. 3 in that a `second reed Yswitch is substituted for themember 13 and `field of the permanent magnet 11. Similarly the switches1 are released when the member 10 is in the opposite state of remanentmagnetization. Suitable insulating means, not shown, is provided to keepthe respective terminals 3 of the two switches 1 electrically isolated.

'It is to be understood that the above-described arrangements areillustrative of the principles of the invention. Numerous otherarrangements may be devised by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. An electrical switching device comprising a magnetically responsiveswitch having oppositely disposed terminals, means adjacent one terminalof said switch comprising a magnetic member of a material exhibiting twostable remanent magnetization conditions for producing a selected one offirst and second oppositely directed 'magnetic fields in said switch,and a permanent magnet positioned adjacent another terminal of saidswitch so that the field of said permanent magnet reinforces said firstmagnetic field and substantially cancels said second oppositely directedmagnetic field in said switch.

2. An electrical switching device in -accordance with claim 1 whereinsaid permanent magnet comprises a first member encircling said other`terminal of said switch and said magnetic member comprises a secondmember encircling said one terminal of said switch.

3. An electrical switching device in accordance with claim 2 whereinsaid means adjacent said one terminal of said switch for producing saidfirst and second magnetic 'fields further comprises a current conductingwinding on sesgos? said switch .remote from said permanent magnet, andfurther comprising magnetically permeable means connecting the ends ofsaid magnetic rmember and said .per-

vmarient magnet remote from said switch, said magneticalneticallyresponsive switch having ya pair of contacts, a

hermetically sealed envelope enclosing said contacts, and a pair ofterminals attached to said contacts and extending outside said envelope;a permanent magnet adjacent said switch for applying a first magneticfield tending to hold said switch contacts in a predetermined position;a magnetic member of a material exhibiting two stable remanentmagnetization states positioned relative to said switch and saidpermanent magnet so that the magnetic eld produced by said magneticmember in one of said remanent magnetization states substantiallycancels said first magnetic iield at said switch; and a winding on saidmagnetic member energizable Ifor establishing one or the other of saidtwo stable remanent magnetization states.

7. An electrical switching device comprising a reed switch havingterminals at opposite ends thereof and a pair of contacts connected tosaid terminals, a first magnetic member of a permanently magneticmaterial adjacent one of said terminals, a second magnetic member or" amagnetic material exhibiting two stable remanent magnetizationstatesadjacent the other of said terminals, said reed switch completinga iirst tiux path betweensaid first magnetic member and said secondmagnetic member, and a winding coupled to said second magnetic memberenergizable for establishing one ofsaid stable remanent magnetizationstates in said second magnetic member 6 to oppose the linx of said tirstmagnetic member and open said switch contacts, said winding also ybeingenergizable for establishing the other of said magnetization states insaid second magnetic member to reinforce the linx of said permanentmagnet and close said switch contacts.

8..An eiectrical switching device in accordance with claim 7 and furthercomprising magnetically permeable means connecting said iirst and secondmagnetic members, said magnetically permeable means completing a secondux path between said last-mentioned members.

9. An electrical switching device in accordance with claim 8 whereinsaid magnetically permeable means comprises an additional reed switch insaid second ux' path.

i l0. A switching device comprising a iirst magnet of permanent magneticmaterial, a second magnet of a material exhibiting more than one stable`state of remanent magnetization, a relay positioned in the magneticfields established lby said iirst and second magnets, and means foractuating said relay comprising means for changing the stable state ofremanent magnetization of said second magnet whereby the magnetic iieldof said second magnet selectively aids or opposes the magnetic iield ofsaid first magnet.

11. An electrical switching device comprising a magnetically lresponsiveswitch, a permanent magnet, and a magnetic member of a materialexhibiting a plurality of vstable remanent magnetization statespositioned in a common magnetic circuit, and means lfor actuating saidswitch in one discrete time interval comprising means for establishingya predetermined one of said magnetization states of said magneticmember in a preceding discrete time interval.

References Cited in the tile of this patent UNITED STATES PATENTS

